[erlang-questions] Reproducible Erlang builds - still some time stamps (non-deterministic build)

[Jesper Louis Andersen]

I don't think it is good to remove modules from the OTP installation and
then proceed to call it Erlang/OTP. Likewise, it is bad to split OTP into
many submodules so people can mix'n'match subparts of the installation.
Often, this adds another step for newcomers to the language since they are
missing important parts of the installation.

I'd much rather you patch the affected files. For instance by replacing the
timestamps with SHA256 checksums ( crypto:hash(sha256, File) ), since this
will still make the files change, yet be deterministic in their generation.


On Tue, Jun 14, 2016 at 11:43 AM, Mikael Pettersson <mikpelinux@REDACTED>
wrote:

> Pjotr Prins writes:
>  > Dear all,
>  >
>  > At http://biobeat.org/report.html a diffoscope of two builds on GNU
>  > Guix of Erlang 19.0-rc2 (made by leo). It turns out some files are
>  > still different between builds. Some .script files contain time stamps
>  > like:
>  >
>  >     %% script generated at {2016,6,11}{19,5,37}
>  >
>  > The snmp, otp_mips, os_mon, gs modules also injects time stamps.
>  >
>  > And some beam files in cosNotification and cosProperty introduce
>  > differences.
>  >
>  > I think none of these modules is critical and we can safely purge
>  > these modules from GNU Guix so it becomes deterministic (we only
>  > accept deterministic software packages) for the time being. Do you
>  > agree?
>
> No.
>
> I acknowledge your need for deterministic builds, but the solution
> ought to be to eliminate the source of the non-determinism, not the
> files themselves.  So:
>
> 1. Patch whatever inserts these time stamps to not do that, or
> 2. Post-process affected files and remove the time stamps.
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-- 
J.
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